Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom.
Protist. 2012 Jul;163(4):602-15. doi: 10.1016/j.protis.2011.10.010. Epub 2011 Dec 18.
Trypanosomes and Leishmanias are important human parasites whose cellular architecture is centred on the single flagellum. In trypanosomes, this flagellum is attached to the cell along a complex flagellum attachment zone (FAZ), comprising flagellar and cytoplasmic components, the integrity of which is required for correct cell morphogenesis and division. The cytoplasmic FAZ cytoskeleton is conspicuously associated with a sheet of endoplasmic reticulum termed the 'FAZ ER'. In the present work, 3D electron tomography of bloodstream form trypanosomes was used to clarify the nature of the FAZ ER. We also identified TbVAP, a T. brucei protein whose knockdown by RNAi in procyclic form cells leads to a dramatic reduction in the FAZ ER, and in the ER associated with the flagellar pocket. TbVAP is an orthologue of VAMP-associated proteins (VAPs), integral ER membrane proteins whose mutation in humans has been linked to familial motor neuron disease. The localisation of tagged TbVAP and the phenotype of TbVAP RNAi in procyclic form trypanosomes are consistent with a function for TbVAP in the maintenance of sub-populations of the ER associated with the FAZ and the flagellar pocket. Nevertheless, depletion of TbVAP did not affect cell viability or cell cycle progression.
锥虫和利什曼原虫是重要的人体寄生虫，它们的细胞结构以单个鞭毛为中心。在锥虫中，这条鞭毛通过一个复杂的鞭毛附着区（FAZ）附着在细胞上，该区域由鞭毛和细胞质成分组成，其完整性对于正确的细胞形态发生和分裂是必需的。细胞质 FAZ 细胞骨架与内质网的一片称为“FAZ ER”明显相关。在本工作中，使用血液阶段锥虫的三维电子断层扫描来阐明 FAZ ER 的性质。我们还鉴定了 TbVAP，这是一种 T. brucei 蛋白，在 Procyclic 形式细胞中通过 RNAi 敲低会导致 FAZ ER 以及与鞭毛口袋相关的 ER 显著减少。TbVAP 是 VAMP 相关蛋白（VAPs）的同源物，是完整的内质网膜蛋白，其在人类中的突变与家族性运动神经元疾病有关。标记的 TbVAP 的定位和 TbVAP RNAi 在 Procyclic 形式锥虫中的表型与 TbVAP 在维持与 FAZ 和鞭毛口袋相关的内质网亚群中的功能一致。然而，TbVAP 的耗竭并不影响细胞活力或细胞周期进程。
